In order to meet requirement of a data center, a stacking system consists of a core backbone (CB)-port extender (PE) is proposed. In the stacking system, CB devices are connected with each other in a ring or in a chain via stacking links. A PE device is connected with a CB device via a stacking link. PE devices are not connected with each other.
In the stacking system, the PE device provides a port extension function for the CB device. The CB device learns a forwarding table entry based on a source address (e.g., learns the forwarding table entry based on a media access control (MAC) address), searches for a forwarding table entry matching a destination address, and determines an identifier of a destination forwarding chip and a destination port for forwarding a packet.
In the whole stacking system, different global identifiers are assigned to forwarding chips of the CB devices and the PE devices. If the identifier of the destination forwarding chip corresponds to a forwarding chip of the PE device, the CB device transmits a packet containing the identifier of the destination forwarding chip and a destination port number to the PE device. The PE device forwards the packet via the corresponding forwarding chip and destination port number.